1. Field of the Invention
The present invention relates to the compression of a digital video signal, and more particularly, to an apparatus and method for controlling a variable bit rate (“VBR”) in a video recording system, such as, for example, a digital camera or a digital camcorder, in real time.
2. Description of the Related Art
An output bit stream meeting a digital video compression standard, such as, for example, MPEG-2, MPEG-4 or H.263, may be used with a constant bit rate (“CBR”) or a variable bit rate (“VBR”), according to the purpose.
A CBR encoding has been extensively used because it is a simple process, but it is disadvantageous in that the quality of an image is lowered in an actual video sequence having a severe fluctuation between frames. On the other hand, VBR encoding enables variable and effective allocation of bits in a limited storage space, thereby regularly maintaining the quality of an image and enabling the effective compression of the encoding.
In general, a two-step quantization is required in a method of controlling the VBR: an optimum quantized parameter is detected and selected in the first step; and quantization is actually performed using the selected quantized parameter in the second step. The method of controlling the VBR is useful in detecting the optimum quantized parameter, but a delay in the encoding may be caused during which the two-step quantization is performed. Therefore, this method is not appropriate for application to a system of compressing and storing video data in real time.